The present invention relates to processing of a semiconductor device, and more particularly, but not exclusively relates to a technique to selectively perfom a self-aligned silicide process on polysilicon structures of an integrated circuit.
Ohmic resistors are basic components of many Integrated Circuits (ICs). They are of particular importance for analog devices and hybrid devices that mix digital and analog circuitry. One of the simplest forms of resistors is a heavily doped polysilicon line. Such lines may exhibit a sheet resistance of between about 100 to 300 Ohms per square --suitable to make resistors that occupy a relatively small area. In a self-aligned silicidation, sometimes called "SALICIDE," the polysilicon lines may not ordinarily be used as resistors, because the silicidation process drastically lowers the sheet resistance of the polysilicon to a value of less than 10 Ohms per square. With such low resistance for the silicided polysilicon, the excessive area required to form a silicided resistor compared to a polysilicon resistor without silicide is prohibitive.
Thus, there is a need for a technique to provide polysilicon resistors by selectively excluding silicide formation in a simple and cost effective manner without jeopardizing silicide formation where it is desired. The present invention meets this need and provides other significant benefits and advantages.